A. W. JEwell — Rotatory Polarizatio??. 369 



Dec. 28. Independent jelly cylinder. Length = 7*0 diam.= 1*8. 



Twist 210 —220 



Rotation — 10 11 



Rubber tube slipped over : 



Twist —240 130 



Rotation 30 —13 



The rotation for a given twist is increased by increasing 

 the envelope. 



July 21, '02. Jelly tube. Length (of jelly in tube) = 3'0. Lower 

 clamp free (i. e., suspended from jelly tube and not resting on 

 the platform e). 



Twist —120 120 



Rotation... _ 8 — 4 



Wrapped tightly with thin rubber : 



Twist -120 120 



Rotation 21 —30 



Thin rubber wrapping replaced by a second rubber tube 

 slipped over first rubber tube : 



Twist 120 —120 



Rotation —26 11 



Longitudinal Compression and Elongation. — It was early 

 noticed that longitudinal compression increased the rotation of 

 the plane of polarization for a given twist, while longitudinal 

 elongation decreased it. Measurements of this effect with the 

 final form of apparatus are given below. The lower clamp 

 was twisted through an angle, read with the graduated circle, 

 v, and pointer, h (see fig. 1) and clamped to the platform e by 

 the clips g. The compression or elongation was applied by 

 raising or lowering this platform by the screws f. The length 

 of the jelly tube was taken as the distance between two pin 

 points, pricked into the rubber tubing outside the glass disks I. 

 Decrease in length we will take as positive and increase as 

 negative. 



I. Aug. 2, '02. Jelly tube C 5. Original length =3'33. Twist 



of —90. 

 Change in length 



(m.m.) -5 1-2 — '5 — VI —3'9 —4'5 — 2'7 



Rotation 19 26 33 19 16 8 2 1 3 18 



II. Aug. 4. Same tube. Twist =. 90. (All rotations negative.) 



Change in length.. 0-9 2 —-8 — VI —2 -4-9 — *1 

 Rotation 18 27 43 16 11 5 4 21 



